The masked gunman who killed two people in the crowded Clackamas Town Center mall in suburban Portland, Ore., was identified today as Jacob Tyler Roberts.

Roberts, 22, was armed with a stolen AR-15 semi-automatic weapon, Sheriff Craig Roberts told a news conference today. He was not wearing a bullet-proof vest as previously reported.

Earlier today the sheriff told "Good Morning America" the gunman was intent on killing "as many people as possible."

"At this time we do not understand the motive of this attack except to say no apparent relationship between suspect and victims," the sheriff said at the news conference.

The shooter, wearing a white hockey mask and black clothing, tore through the mall just before 3:30 p.m. Tuesday, entering through a Macy's store and heading to the food court and public areas spraying bullets, according to witness reports.

"We have been able to identify the shooter over this last night," Roberts said. "I believe, at least from the information that's been provided to me at this point in time, it really was a killing of total strangers. To my knowledge at this point in time he was really trying, I think, to kill as many people as possible."

Police said today that Roberts had stolen the gun from someone he knew, and was equipped with a load bearing vest and "several" fully loaded magazines. Police are still trying to determine how many shots were fired.

Roberts' mother, Tami Roberts, released a statement through a friend today saying she had no explanation of her son's behavior.

"Tami Roberts wishes to express her shock and grief at the events at Clackamas Town Center Tuesday," the friend said, reading from a statement outside of Tami Roberts' home. The woman identified herself as Holly but declined to give her last name, and said she was Tami Roberts' best friend.

The friend noted that Tami raised Roberts, but was not his biological mother.

"She has no understanding or explanation for her sons behavior and request that her privacy be respected. She is very sad and wants everyone to know she is so sorry for what Jake did. It's so out of his character," Holly said.

Roberts, who attended Clackamas Community college, said on his Facebook page that he worked in a gyro shop in downtown Portland and posted a picture of himself firing a gun at a target. His Facebook photo showed graffiti in which the words "Follow Your Dreams" were painted over with the word "Cancelled."

School officials at Milwaukie High School, where Roberts attended from 2004 to 2007, describe him as an "average student with average grades." He had no disciplinary record at the school, but transferred his senior year to Oregon City High School, according to Joe Krumm, an administrator at the North Clackamas School District. Krumm did not know why he transferred, and said that in all, Roberts did not stand out in memory for anything in particular.

Yuille's family released a statement today calling Yuille a "wonderful person."

"Cindy was everybody's friend, she was a wonderful person, she was very caring and put others first," the family said, noting that they needed time to grieve their loss.

Forsyth, who owned a business at the mall, was described as a married father of two.

"Steve was one of most passionate people, with an entrepenurial spirit that led him to start his business," the family said in a statement. They said he had a "zest for life, a vision and belief in others that brought great joy.."

A third shooting victim, Kristina Shevchenko, 15, was taken to a hospital and has undergone an initial surgery, according to a Facebook page set up by her family members. Family members said she was hit in the back, and a bullet bruised her lung but avoided piercing any major organs.

Police said today that Roberts parked his car outside of the Macy's department store, entered the mall on the second floor, and then "moved quickly" toward the food court, firing shots. Yuille and Forsyth were hit by bullets near the food court, police said. Other shoppers provided medical aid to the victims.

Roberts' gun jammed briefly while shooting at the food court, but he was quickly able to resume shooting, police said.

Roberts then ran down a hallway and a flight of stairs to the first floor of the mall, near an REI store, where he apparently shot himself, police said.

Shevchenko was hit on the second floor but made it outside to the first floor, where she met police and was taken to the hospital, police said.

Investigators searched Roberts' home and car in the wake of the shooting, but did not disclose what they found. They confirmed that his fingerprints matched prints in a law enforcement database, though they did not find any crimes he was convicted of.

Sheriff Craig Roberts said that he believed that the gun jamming, in addition to the quick response of mall employees to enact lockdown procedures, prevented more individuals from being shot and killed during the spree.

The sheriff said that the first calls of gunshots came in at 3:29 p.m. and the first police officers to respond arrived a minute later at 3:30 p.m.

"Officers initiated an active shooter protocol, a technique we train with, and equipped each of our officers to move to immediately engage the threat wherever it might be. We were well prepared for this incident. We had practiced active shooter techniques at Clackamas Town Center earlier this year. We had practiced for just this type of situation," the sheriff said.

By 4:40 p.m., police reported finding a group of people hiding in a storeroom. In a surreal moment, even the mall Santa was seen running for his life.

"I didn't know where the gunman was, so I decided to kind of eased my way out," said the mall Santa, who the AP identified as 68-year-old Brance Wilson.

Cell phone video shot at the scene shows the chaos soon after the shooting. When police arrived they were met head on by terrified shoppers, children and employees streaming out. Customers, even a little girl, were being lead out with their hands up.